This invention relates to lithography and more particularly to soft x-ray lithography.
Lithography is a process of replicating a pattern on a material. Heretofore lithograhy has been carried out by the use of electrons, light, ultraviolet radiation and x-ray radiation from electron impact and synchrotron sources. In photolithography, light is passed through a mask containing the pattern of interest to a substrate sensitive to light. Light suffers diffraction effects which degrade the replication when fine-scale (about 1 .mu.m) features are present in the mask. X-rays have wavelengths sufficiently small that diffraction effects are negligible. In x-ray lighography, the mask consists of a thin sheet of x-ray-transparent material such as beryllium, silicon or a plastic-like substance supporting a pattern of x-ray absorbing material, usually gold. The substrate is coated with an x-ray sensitive material called x-ray resist. Electron-impact x-ray sources used in the prior art generally produce high-energy x-rays above 5 keV which are not stopped in the thin x-ray resist. Therefore the substrate is damaged. Synchrotron sources emit softer x-rays. However, these x-ray devices are expensive and usually very large and bulky so these are not suitable for routine production of x-ray lithographic replicas.